1. Field of the Invention
The systems and methods of this invention relate to pacing treatment of the heart comprising applying vibrational energy.
Heart Failure (HF) currently affects over 5 million patients in the United States alone. This population has been steadily increasing due to overall demographic aging and, in particular, the effects of new life-prolonging treatments to patients with chronic cardiac conditions. HF is defined by ACC/AHA Task force as a complex clinical syndrome that impairs the ability of the ventricle to fill with or eject blood. New medications developed to treat HF have been generally ineffective, and device-based solutions appear to present a significant opportunity for afflicted patients.
HF generally results from one or more underlying factors including hypertension, diabetes, valvular disease, cardiomyopathy, coronary artery disease, or structural changes to the heart muscle. HF is characterized by reduced ventricular wall motion in systole and/or diastole, and low ejection fraction. As the heart becomes less able to pump sufficient volume to the system, patients develop symptoms of fluid retention, shortness of breath, and fatigue.
Approximately one third of patients with HF have poor timing of contraction between the right and the left ventricle and within the left ventricle, called interventricular and intraventricular dyssynchrony, respectively. This is sometimes also manifest by a wider than normal QRS interval on a surface electrocardiogram (ECG) taken of a HF patient. The wider than normal QRS interval is called conduction delay because there is a prolonged time interval for the normal electrical impulse to travel (“conduct”) to all parts of both ventricles. This is also sometimes manifest by conduction delay between the atria and ventricles (A-V delay). Ventricular dyssynchrony and conduction delays can contribute to weak left ventricular function by causing delayed and/or abnormal left ventricular contraction. There may be inadequate filling and emptying of the left ventricle, as well as backflow of blood into the left atrium, resulting in decreased cardiac output and increased symptoms for the patient. This dysfunction causes increased mortality and morbidity among patients with HF.
Cardiac resynchronization therapy is the use of pacing to coordinate the contraction of the ventricles in order to reduce heart failure and improve prognosis in HF patients. Recently, devices that pace both ventricles, referred to as bi-ventricular pacing, have been adopted to provide cardiac resynchronization therapy. A bi-ventricular pacing system utilizes conventional dual chamber, right atrium and right ventricle, pacing technology but adds a third lead, usually in a coronary vein, to sense and pace the epicardial surface of the left ventricle. The pacing device can then, at an appropriate time interval after right atrial activity, synchronize contraction of both right and left ventricles either simultaneously or at coordinated time intervals. The synchronous contraction of the ventricles facilitates more adequate filling of the left ventricle and less backflow (mitral valve regurgitation to the left atrium), resulting in more oxygenated blood being pumped to the body. Alternatively, it has been shown that pacing only the left ventricle at a location near the apex is associated with improvement in left ventricular function. However, this location is not accessible from the coronary veins in current pacing systems.
Clinical studies have shown a sustained improvement of symptoms and exercise tolerance in patients using bi-ventricular pacing devices to improve left ventricular function. Cardiac resynchronization therapy has also been incorporated into implantable cardioverter defibrillator (ICD) devices, allowing for the simultaneous treatment of heart failure and the prevention of sudden cardiac death caused by life-threatening ventricular arrhythmias in HF patients.
Pacemaker leads are typically placed through the skin into a subclavian vein to access the venous side of the cardiovascular system. In bi-ventricular pacing systems, one lead is placed in contact with the right ventricular wall and one lead is placed in contact with the right atrial wall. To access the left ventricle, the third lead is passed into the right atrium, into the orifice of the coronary sinus, and then maneuvered through the coronary veins to a position on the epicardial aspect of the lateral wall of the left ventricle. Some work has been done exploring minimally invasive methods of alternatively placing the lead/electrode directly on the epicardium of the left ventricle.
Placement of the third lead to contact the left ventricle has been a significant problem for application of this therapy. The coronary sinus is a complicated venous pathway with multiple branches which bend and narrow with considerable variation as they extend distally onto the epicardium of the left ventricle. Placement of this lead requires significant skill on the part of the physician. In order to provide adequate steerability and pushability, the design of the left ventricular lead or a lead introduction system/device is much more complicated than for regular pacing leads. Often the left ventricular lead positioning/placement can take over an hour to perform exposing the patient to increased fluoroscopy radiation and increased procedure risks. Furthermore, in some patients (7.5% in the MIRACLE study), an acceptable lead placement is not possible due to anatomic constraints or undesirable phrenic nerve pacing. Additionally, lead dislodgement and loss of pacing capture have been a common complication in the use of these coronary sinus leads (e.g., 10–20% complication rates have been reported within the first 6 months of device placement).
It would be beneficial to eliminate the third pacing lead and yet provide resynchronization within the left ventricle and/or between the left and right ventricles. Moreover, it would be beneficial to provide more physiological pacing of the right ventricle. In normal physiology, the right ventricle is first stimulated in the upper septal area, and then the impulse travels down specially conducting pathways to the right ventricular apex. However, pacing from the right ventricle is virtually always accomplished from a lead tip located in the right ventricular apex, such that the conduction pathway is abnormal and slow. Clinical trials have recently shown that in patients with and without A-V block, pacing from the right ventricular apex can result in increased total mortality and re-hospitalization for heart failure compared to non-paced patients. The possible adverse effects of pacing the right ventricular apex in patients without bi-ventricular pacemakers is unknown, but a source of growing concern.
2. Description of the Background Art
This application has disclosure related to prior commonly assigned provisional applications 60/479,347, filed on Jun. 17, 2003; 60/496,184, filed on Aug. 18, 2003; 60/496,179, filed on Aug. 18, 2003; and 60/507,719, filed on Sep. 30, 2003. The full disclosures of each of these prior filings are incorporated herein by reference.    U.S. Pat. No. 4,928,688/RE38,119 Mower; Method and apparatus for treating hemodynamic dysfunction.    U.S. Pat. No. 5,174,289 Cohen: Pacing systems and methods for control of the ventricular activation sequence.    U.S. Pat. No. 5,018,523 Bach et al.; Apparatus for common mode stimulation with bipolar sensing.    U.S. Pat. No. 6,070,101 Struble et al.; Multiple channel, sequential, cardiac pacing systems.    U.S. Pat. No. 6,439,236 Porter and Xie; Methods of inducing atrial and ventricular rhythms using ultrasound and microbubbles.    PCT WO 03/070323 Adam et al; Ultrasound Cardiac Stimulator.    U.S. Pat. No. 6,223,079 Bakels et al.; Bi-ventricular pacing method.    U.S. Pat. No. 4,651,716 Forester et al.; Method and device for enhancement of cardiac contractility.    PCT WO 9961058 Van der Wouw; Method of altering heart beat.    ACC/AHA Task Force on Practice Guidelines. Evaluation and Management of Chronic Heart Failure in the Adult. JACC 2002;38:2101–13.    Daubert et al., “Use of Specifically Designed Coronary Sinus Leads for Permanent Left Ventricular Pacing: Preliminary Experience”, PACE, 1997; 20: II-NASPE Abstract 17, April, 1997.    Leclerq C et. al., “Acute Hemodynamic Effects of Biventricular DDD Pacing in Patients with End-Stage Heart Failure”, JACC 1998;32:1825–1831.    Daubert et al., “Permanent Left Ventricular Pacing With Transvenous Leads Inserted Into The Coronary Veins”, PACE 1998;21;239–245.    Daoud et al., “Implantation Techniques and Chronic Lead Parameters of Biventricular Pacing Dual-chamber Defibrillators”, J Cardiovasc Electrophysiology 2002; 13:964–970.    Valls-Bertault et al., “Adverse Events with Transvenous Left Ventricular Pacing in Patients with Severe Heart Failure: Early Experience from a Single Centre”, Europace 2001;3:60–63.    Leclercq C et al., “Systolic Improvement and Mechanical Resynchronization does not Require Electrical Synchrony in the Dilated Failing Heart with Left Bundle-Branch Block”, Circulation 2002; 106:1760–1763.    Linde C et al., “Long-Term Benefits of Biventricular Pacing in Congestive Heart Failure: From the Multisite Stimulation In Cardiomyopathy (MUSTIC) Study”, J Am Coll Cardiol 2002;40:111–118.    Abraham W T et al., “Cardiac Resynchronization in Chronic Heart Failure”, N Engl J Med 2002;346: 1845–1853.    Bradley D J et al., “Cardiac Resynchronization and Death from Progressive Heart Failure: A Meta-Analysis of Randomized Controlled Trials,” JAMA 2003;289:730–740.    Nielsen J C et al., “A Randomized Comparison of Atrial and Dual-Chambered Pacing in 177 Consecutive Patients with Sick Sinus Syndrome,” J Am Coll Cardiol 2003;42:614–623.    DAVID Trial Investigators, “The Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial,” JAMA 2002;288:3115–3123.    MIRACLE Trial Investigators, “Combined Cardiac Resynchronization and Implantable Cardioversion Defibrillation in Advanced Heart Failure: the MIRACLE ICD Trial,” JAMA 2003 ;289:2685–2694.